What does a dry chemical extinguisher do to suppress a fire?

• A. It interferes with the chemical reactions occurring in the flame and coats the fuel to prevent ignition.
• B. It heats the fuel to promote combustion.
• C. It seals leaks in pipes.
• D. It increases the oxygen concentration in the air.

Answer: (A)

Dry chemical extinguishers work by interrupting the chemical reactions happening in the flame and by coating the fuel surface to keep the fuel from re-igniting. The powder interferes with the flame’s chemical processes, effectively stopping combustion, and the coating acts as a barrier that slows or prevents re-ignition once the flames are knocked down. This is why the option describing interference with flame chemistry and a coating on the fuel is the best fit. The other ideas—heating the fuel to promote combustion, sealing leaks, or increasing the oxygen in the air—do not align with how dry chemical extinguishers suppress fires.